Re: TimeStampedData draft updated


Adriano,

Thank you for this new proposal. I skimmed through it.

It is interesting, but I fear that it is targeted to the wrong WG.
Since this would be an extension of CMS, this work item 
would rather belong to the S-MIME WG.
For this reason, I copy the S-MIME WG. 

In addition, some polishing would be needed.

Rather than long words, you will find hereafter a rewriting of the ASN.1 
with a few explanatory comments.

   TimeStampedData ::= SEQUENCE { 
      version        [0] Version DEFAULT v1, 
      fileName           UTF8String, 
      mimeType           PrintableString, 
      fileLocation       UTF8String OPTIONAL, 
      -- fileLocation is only a hint. 
      -- The file may or may not be stored at that location.
      content            OCTET STRING, 
      temporalEvidences  TemporalEvidences 
}

   Version  ::=  INTEGER  { v1(0) } 
   TemporalEvidences ::= SEQUENCE (SIZE(1..MAX)) OF TemporalEvidence 

-- This structure allows multiple levels of temporal evidences.

   TemporalEvidence ::= SEQUENCE {
      evidences            Evidences,
      certificateLists     CertificateLists  OPTIONAL
}

   CertificateLists :: = SEQUENCE (SIZE(1..MAX)) OF CertificateList

   Evidence ::= CHOICE { 
      timeStamps     [0] SEQUENCE (SIZE(1..MAX)) OF TimeStampToken }

-- For each level there can be one or more time-stamps tokens.

-- Before re-time stamping a set of former time-stamp tokens, 
-- the CRLs of the previous level of time-stamps tokens can be captured 
-- and inserted in the data structure.

Denis

Hello there,

here I am again with my TimeStampedData proposal.

I have submitted a new draft (also attached here) that takes into account some 
of the remarks and suggestions received so far.

I have made room for additional types of temporal evidence, like e.g. RFC 
4998, while keeping RFC 3161 as the basis of interoperability.

I would like to invite everybody involved in time-stamping and archiving 
e-documents to comment upon it: has it improved? something is missing?

In particular, please state:
- are you interested in this work?
- do you agree to adopt it as a new PKIX work item?
- are you going to use this format, once it is finished?

Is anybody willing to spend a few words on this draft during the IETF meeting 
in Vancouver (as I cannot attend myself) ?

And finally, is anybody willing to invest a little time in co-authoring this 
draft with me?

Adriano
Actalis S.p.A.
Milano, ITALY




-----Messaggio originale-----
Da: owner-ietf-pkix(_at_)mail(_dot_)imc(_dot_)org 
[mailto:owner-ietf-pkix(_at_)mail(_dot_)imc(_dot_)org] Per conto di Santoni 
Adriano
Inviato: lunedì 3 settembre 2007 10.42
A: ietf-pkix(_at_)imc(_dot_)org
Oggetto: R: R: Draft on TimeStampedData


Let me summarize the issues discussed so far:

1) allow EvidenceRecord (RFC 4998) in addition to TimeStampToken (RFC 3161)

In principle, I have no objections as long as we do not complicate things too 
much and do not hamper interoperability. 

There are at least two possible approaches to accomodate RFC 4998:

  a) explicitly provide for (one) ER in the TimeStampedData syntax, as an 
alternative to the SET OF TimeStampToken;
  b) do not mention any specific standard for the "evidence", but just 
mention RFC 3161 and RFC 4998 as two possibilities;

In any case, it must be possible for the verifying application to easily 
detect which of the two (or more) kind of "evidence" has been used in the 
TimeStampedData envelope under examination. If we restrict the kinds of 
evidence to the two above, then a extra tagging may not be necessary, as an 
EvidenceRecord is a SEQUENCE, while the other choice would be a SET OF. 
Although unelegant, it would work. On the other hand, if we do not want to 
restrict the kinds of evidence to the two above, then of course we should 
somehow add an extra tagging level, because nobody knows at this time what 
syntax a third kind of evidence would conform to.

In any case, for the sake of interoperability, strong emphasis should be given 
to RFC 3161 as today this is the most widely implemented type of evidence.

In conclusion: I agree with allowing RFC 4998 if we do that in a way that does 
not modify the strong emphasis on RFC 3161 and does not hamper 
interoperability (which must be based on supporting RFC 3161, even though 
certain applications may also support RFC 4998).

2) filename vs. URI 

Some remarked that an URI (or URI Reference) would be more versatile than a 
simple filename. That is obviously true, but it implies that the 'content' 
field of TimeStampedData may be empty. This is not what I was addressing in my 
original proposal. It would not just require the 'content' field to be 
declared OPTIONAL: it would make interoperability very difficult to achieve 
unless we restrict the URI schemes to a very small subset (e.g. http:, cid:, 
file:, ldap:) of the myriad possibilities. In any case, it would require ages 
of interoperability testing. And it would make life much harder for software 
implementors, without much of a benefit in view. I strongly believe in keeping 
things simple as much as possible.

3) multiple contents and RFC 4073

The 'content' field in the TimeStampedData envelope is not structured, in my 
original proposal. It is just an OCTET STRING. That allows for any kind of 
content to be conveyed, even a ContentCollection according to RFC 4073.

Another remark has been made with reference to RFC 4073: the 
ContentWithAttributes structure, also defined in RFC 4073, could in principle 
be used to bundle some content with the corrisponding evidence (the goal of my 
draft). Although this is true, it would require definining some additional 
OIDs, and mandating the presence of certain Attributes tagged by those OIDs. I 
frankly believe the TimeStampedData structure that I am proposing is better, 
first because it is dedicated and second because it "implements the 
ContentInfo interface", so to speak. It is simpler to manage for applications 
already able to parse different kinds of ContentInfo envelopes (there are a 
great many), possibly in a recursive way.

Adriano 


-----Messaggio originale-----
Da: Young H Etheridge [mailto:yhe(_at_)yhetheridge(_dot_)org]
Inviato: venerdì 31 agosto 2007 17.48
A: Santoni Adriano
Cc: ietf-pkix(_at_)imc(_dot_)org
Oggetto: Re: R: Draft on TimeStampedData

Adriano,

To add to your thought processes:  I believe that a URI of 
"file:///private.stuff" addresses your concern for privacy of the physical 
URI.  But, allowing URI in the syntax will make less private repositories, not 
necessarily file systems, more universally accessible.  The intent of the URI 
in RFC 3986 is to also allow for abstractly identifying a resource, not 
necessarily providing a physical resource.  In this manner the URI could then 
be used as an object identity in database(s).

Take care,

yhe

Santoni Adriano wrote:

To accomodate for RFC 4998, I would propose the following syntax:

TimeStampedData ::= SEQUENCE {
     version                 INTEGER { v1(1) },
     fileName                UTF8String,
     mimeType                PrintableString,
     content         OCTET STRING,
     evidence                Evidence
}

Evidence ::= CHOICE {
     timeStamps              [0] SET (SIZE(1..MAX)) OF TimeStampToken,
     evidenceRecord  [1] EvidenceRecord -- according to RFC 4998
}

(I am not sure whether it would be better to use explicit or implicit
tags...)

Regarding the idea of having an URI instead of a filename: I'd prefer to 
think over things a little bit more, and maybe collect more feedback.

In my mind, I can send a TimeStampedData envelope to business partners 
and/or public agencies via email. If the timestamped document is a local 
one, which I think is a meaningful and realistic scenario, then I do not 
want my company's hostnames and pathnames to be included in the envelope so 
that the recipient can see them.

Adriano



-----Messaggio originale-----
Da: owner-ietf-pkix(_at_)mail(_dot_)imc(_dot_)org 
[mailto:owner-ietf-pkix(_at_)mail(_dot_)imc(_dot_)org]
Per conto di Julien Stern
Inviato: venerdì 31 agosto 2007 13.43
A: ietf-pkix(_at_)imc(_dot_)org
Oggetto: Re: Draft on TimeStampedData


On Fri, Aug 31, 2007 at 12:06:00PM +0200, Tilo Kienitz wrote:

Adriano,

After pondering on this and other remarks, I cannot help but agree 
with Steve.

My original and essential goal is that of facilitating 
interoperability in a currently unregulated field. If we allow for 
several "degrees of freedom", than interoperability will be hampered from 
the beginning.
So I'd better stick to RFC 3161 for now. We could include support 
for RFC 4998 Evidence Records later on, at the time when they become 
a widespread reality comparable to RFC 3161 TimeStampTokens (which 
are widely implemented).

I would prefer to have both options: RFC 3161 and RFC 4998. For our 
customers evidence records are a widespread reality already.
A standardized way to put some data and their evidence record into a 
single file would be useful.


I strongly concur with this comment. Allowing the usage of ERS as well as 
simple timestamps would allow the TimestampedData to leverage all the work 
of RFC 4998 regarding timestamps instead of reinventing the wheel in the 
future.

Regards,

--
Julien

Kind regards
Tilo

-----Messaggio originale-----
Da: Stephen Kent [mailto:kent(_at_)bbn(_dot_)com]
Inviato: giovedì 30 agosto 2007 23.05
A: Young H Etheridge
Cc: Santoni Adriano; ietf-pkix(_at_)imc(_dot_)org
Oggetto: Re: R: Draft on TimeStampedData

At 4:33 PM -0400 8/30/07, Young H Etheridge wrote:

...

Agreed, w.r.t. normative vs informative.  The above quote from
RFC-4998 merely underscores that this draft should also suggest, 
informatively, that the choice of Timestamp should be one that 
meets the normative syntax for Timestamp and not specify that which 
is in RFC-3161.  Nothing gets broken by being less restrictive and 
generally more informative to the community-at-large.

I have to disagree with your conclusion. If we require 3161 time stamps in 
an RFC of the sort Adriano proposed, then everyone can parse them if they 
comply with the RFC. If the RFC says "insert the time stamp from any 
standard you want here, and just tell us which one you used" then we have 
a problem. A compliant implementation can generate data structures 
containing time stamps that other compliant implementations cannot parse. 
That's the sort of interoperability problem we try to avoid in the IETF.

My notion of resilience does not mean "more encompassing" but that 
of providing the user community with choice and an enhanced 
safeguard against the possibility of the weakening of an algorithm.

Choices can be good, but they can create interoperability problems in some 
cases, like this one. Also, we have algorithm agility as a requirement in 
all of our work, so the second concern you cite does not seem to apply 
here.

Steve

--
Tilo Kienitz
SecCommerce Informationssysteme GmbH
Obenhauptstr. 5
D - 22335 Hamburg
Germany                                   http://www.seccommerce.de

Re: TimeStampedData draft updated - please comment